Ali Bey el-Abbassi (علي باي العباسي), was the false name/pseudonym that Domènec Badia i Leblich (Barcelona 1766 – Syria 1818), a spaniard explorer and spy in the early 19th century, used for several years in his travels to North Africa and the Middle East. Notably, he witnessed the Saudi conquest of Mecca in 1807.

After receiving a liberal education, Badía devoted particular attention to the Arabic language, which he studied in Valencia and London, and made a special study of the manners and customs of Arabian lands. Under the name of Ali Bey al-Abbasi, pretending to be a descendant of the Abbasid Caliphs of the West, and in Muslim dress, he spent two years (1803-5) in Morocco on terms of high favor with the emperor. He then went to Mecca, at that time in the possession of the Wahabites, ostensibly to perform the hajj. On his way there, he stopped in Tripoli, Cyprus, and Egypt. On his way back, he stopped in Jerusalem and prominent places in Syria, and reached Constantinople in the autumn of 1807.